Vapor condensing apparatus



y 1968 K. H. WIEGMANN ET AL 3,381,746

VAPOR CONDENSING APPARATUS Filed Dec. 16, 1966 8e- 46 Fi .2. I

Karl HJ Viegmcnn John H. Lecr'z r INVENTORS AM. a

ABTRAT BF THE DISCLOSURE A vapor condenser having a hollow housingadapted to be evacuated to sub-atmospheric pressure and in which atubular refrigerated condenser unit is spaced from the housing peripheryand forms with the latter inner and outer chambers which communicatewith each other at the front end of the housing. A vapor inletcommunicates the inner chamber at the rear end of the housing with asource of vapor to be condensed, and a vapor outlet communicates theouter chamber, also at the rear end of the housing, with a source ofsub-atmospheric pressure. Thus, vapors are caused to pass along thecondenser unit from the inlet to the outlet in a countercurrent flowpath.

Background of the invention This invention relates to vapor condensers,and more particularly to a highly eflicient vapor condenser for use withhigh vacuum freeze drying apparatus.

Vapor condensers heretofore have employed an elongated rectangularhousing containing a multiplicity of transversely spaced, rectilinearrefrigerated plates extending parallel to the uni-directional flow ofvapor through the housing. Baflles sometimes are arranged between theplates to direct the vapor over the plates in the most efficient manner.

This prior arrangement limits the housing to a rectangular shape whichis expensive to fabricate to sufficient strength to withstand therequired sub-atmospheric pressures. Moreover, the arrangement of spacedrectilinear plates tends to build up ice layers adjacent the vapor inletto such an extent as to bridge and close the spaces between plates. Thisblocks the flow of vapor to the rest of the plate surfaces, increasingthe pressure drop from inlet to outlet and correspondingly reducing theefliciency of the condenser. Still further, defrosting of ice from theplates involves excessive non-productive time, and drainage of waterfrom the rectangular housing is ineflicient. The rectangular design ofthe housing also requires excessive space to accommodate a given surfacearea on the condenser plates.

Summary of the invention The present invention achieves the principalobjective of overcoming the disadvantages enumerated heretofore, by acondenser construction which provides a countercurrent flow of vaporfrom a central inlet first over the inner surface of a tubularrefrigerated condenser unit and then in the opposite direction along theouter surface of the condenser unit to an outlet, thereby insuringmaximum extraction of condensables from the vapor.

Specifically, the tubular construction of the refrigerated condenserunit achieves the objective of providing maximum condensing surfacearea, with uniform ice distribution, in a housing which occupies aminimum of space.

The concentric arrangement of the vapor inlet, condenser unit andhousing also exposes the entire length of the apparatus to view througha sight glass in the housing, thereby affording thorough inspection andassuring the maintenance of most etlicient operating conditions.

The concentric construction also minimizes manufacturing cost, allowsthe apparatus to be mounted vertically States Patent or horizontally,and provices maximum eificiency of defrosting and drainage.

The foregoing and other objectives and advantages of the presentinvention will appear from the following detailed description taken inconnection with the accompanying drawings of the preferred embodiment.

Brief description of the drawings FIG. 1 is a view in longitudinalsection of vapor condensing apparatus embodying the features of thepresent invention, the arrows indicating the direction of vapor flow.

FIG. 2 is a sectional view taken on the line 2-2 in FIG. 1, the arrowsindicating the direction of flow of refrigerant fluid through thesections of the condenser unit.

FIG. 3 is a plan view of one of the sections of the condenser unit.

FIG. 4 is a sectional view taken on the line 44 in FIG. 3.

Description of the preferred embodiment Referring to the drawing, thevapor condensing apparatus includes a hollow housing defined by theperipheral wall 10, the rear end wall 12 and the front wall 14.

The housing is shown mounted in horizontal position by means oflongitudinally and laterally spaced legs 16, the lower ends of which aresupported upon a foundation.

In the embodiment illustrated, the front wall comprises a door theperipheral flange 18 of which is mounted pivotally on the peripheralflange 20 at the front end of the housing wall 10, by means of the hinge22. An annular resilient gasket 24 is secured to the flange of the doorfor abutment against the flange 20 to provide a vacuum tight seal. Aplurality of bolts 26 extend through aligned openings in the flanges forsecuring the door releasably in closed position. A central window 28 inthe door affords visual inspection of the interior of the housing.

The hollow housing contains an elongated tubular condenser unit 30spaced inwardly from the peripheral wall 10 of the housing. In thepreferred embodiment illustrated, the condenser unit is formed of aplurality of longitudinally extending sections 30, there being four suchsections shown. As best seen in FIGS. 3 and 4, each section comprises apair of plates 32 within the margins of which are stamped or otherwiseimpressed on their inner sides a serpentine channel. The plates arewelded together about their margains with the serpentine channelsregistering with each other, thereby forming a continuous passageway 34between the open ends which communicate with the projecting tubingcouplings 36. One of these couplings functions by connection with alength of tubing 38 (FIG. 1) to admit refrigerant fluid from a source(not shown) to the passageway, while the other coupling serves, byconnection with another length of tubing 40, to return the circulatedfluid to the source.

The condenser unit sections are joined together along their longitudinalmargins to form the tubular construction illustrated. The margins of theupper and lower sections are overlapped and connected together by suchmeans as the bolts 42. The front end of the unit is supported within thehousing by such means as the upper and lower brackets illustrated. Theupper bracket 44 is secured at one end to the housing and at theopposite end to the overlapping side edges of the condenser unitsections.

The lower bracket assembly includes the base bracket 46 which supportsthe spaced connector brackets 48. These are secured one to each of theadjacent margins of the lower sections. The narrow space between thesemar- 6 gins facilitates defrosting of the condenser unit withoutimpairing its function of providing countercurrent vapor flow describedhereinafter.

The rear end of the condenser unit is spaced slightly from the rear wall12 of the housing on which it is supported by the inwardly projectinglugs 50 and interposed heat insulating spacers 52. It will be understoodthat heat insulating spacers also are interposed between the condensersections and the front brackets 44 and 48 to prevent transfer of coldtemperature from the condenser unit to the housing.

The front end of the condenser unit is open and terminates inwardly ofthe front wall 14 of the housing. The housing and condenser unit thuscooperate to form inner and outer chambers 54 and 56, respectively,which communicate with each other at the front end, for purposesexplained in detail hereinafter.

The four inlet tubiugs 33 connect to a common header 58, the inlet pipe60 of which extends through the housing wall and is fitted at its outerend with a flange 62 by which to connect a feed line from a circulatingsource of refrigerant fluid (not shown). The return tubings 4t:similarly connect to a common header 64 the return pipe 66 of whichextends through the housing wall and is fitted at its outer end with aflange 68 by which to connect a return line to the source of refrigerantfluid.

Extending through the rear wall 12 of the housing and communicating withthe inner chamber 54 within the condenser unit is a vapor inlet conduit7%. This conduit is sealed to the housing wall, as by welding, and itsouter end is provided with a peripheral flange 72 by which to connect avapor infeed line leading from a source (not shown) of vapor to becondensed.

Although the vapor condensing apparatus of the present invention may beutilized for a variety of purposes, it has particular utility inassociation with apparatus for freeze drying foodstuffs andpharmaceuticals. Essentially, this involves the removal of waterremaining in a frozen substance by changing the ice crystals to vaporwithout allowing the ice to melt.

This process of sublimation occurs at sub-atmospheric pressures.Accordingly, the condenser housing is provided with a vacuum outletconduit 74 having a flange 76 at its outer end for connection to avacuum line leading from a vacuum pump (not shown). This outlet conduitcommunicates with the outer chamber 56 defined between the housing andcondenser unit, and is positioned adjacent the rear wall 12 of thehousing. In this manner vapors to be condensed enter the inner chamber54 adjacent the rear wall of the housing and thus are caused to passalong the inner surface of the condenser unit to the forward open end ofthe latter, and thence rearward through the outer chamber 56 and alongthe outer surface of the condenser unit to the outlet conduit 74, asillustrated by the arrows in FIG. 1. This counter current flow of vaporresults in the latter being subjected to the freezing temperature of theentire inner and outer surfaces of the condenser unit, thereby insuringmaximum extraction of condensables from the vapor with only thenon-condensables being exhausted to the vacuum pump.

It is important that the condensables be caused to build up on the innerand outer surfaces of the condenser unit in a substantially uniform icelayer throughout the entire length of the unit. This insures againstblockage of vapor flow, as is inherent in the plate type condenserconstructions of the prior art, and assures maximum operating efficiencyof the apparatus.

Maximum degree of uniformity of build-up of the ice layer along thelength of the condenser unit is achieved, in the preferred embodimentillustrated, by the provision of a vapor distributor. This consists ofan elongated tube 78 which communicates at its open rear end with thevapor inlet conduit 70 and which extends forwardly therefrom in inwardlyspaced relation to the condenser unit. The portion of the distributortube within the condenser unit is perforate, as indicated by themultiplicity of relatively large openings 80. The vapor to be condensedpasses outward through these openings into the space of the innerchamber 54 between the distributor tube and the condenser unit. Thevapors thus are distributed substantially uniformly over the innersurface of the condenser unit. The front end of the distributor tube maybe open, as illustrated, or it may be closed by an end wall if desired.

In the embodiment illustrated, the distributor tube 73 is supported atits rear end by fitting over the inwardly extending portion of the vaporinlet conduit 70, and its front end is supported by means of thebrackets 82 connecting the brackets which support the front end of acondenser unit.

A plurality of conduits are provided through the housing wall it). Oneor more of these may be used to introduce hot water or steam into thehousing for melting ice collected on the condenser unit. The melted iceand water are drained out the bottom of the housing through the valvecontrolled drain pipe 86. Others of the conduits may contain sealedtherrno-couples for measuring the temperature of the condenser unit,While still others may contain sealed vacuum measuring leads formeasuring the sub-atmospheric pressure in the apparatus.

in the operation of the vapor condensing apparatus of the presentinvention, the vapor infeed conduit 70 is connected to freeze drying orother apparatus providing vapor which is to be condensed. The outletconduit 74 is connected to a vacuum pump by which to reduce the pressurewithin the condenser housing and freeze drying or other apparatus to therequired sub-atmospheric ressure. The outlet of a circulating source ofrefrigerant fluid is connected to the inlet pipe 60, and the return pipe66 is connected to the return side of the refrigerant source to providea continuous circulation of refrigerant fluid through the passageways 34in the sections of the condenser unit.

Vapors to be condensed thus are drawn through the infeed conduit and theopenings of the distributor tube. The vapors pass through the innerchamber 54 uniformly along the entire length of the inner surface of thecondenser unit forwardly around the open front end of the latter andthence rearwardly through the outer chamber and along the entire lengthof the outer surface of the condenser unit. condensables in the vaporthus are deposited uniformly over the entire inner and outer surfaces ofthe condenser unit, and non-condensables (air, etc.) are carried throughthe outlet conduit 74 to the vacuum pump.

During the condensing operation visual inspection of the interior of thecondensing apparatus may be made through the sight glass 28 provided inthe door. When the layer of ice collected on the condenser unit reachesa predetermined maximum, above which the efficiency of the apparatus isadversely affected, the pressure in the housing is broken back toatmospheric, and hot water or steam is introduced through one of moreconduits 84 in the housing, to melt the ice on the condenser unit. Themelted ice and water are drained out the bottom of the housing throughthe valve controlled drain pipe 86.

It will be apparent to those skilled in the art that various changes maybe made in the size, shape and arrangement of parts describedhereinbefore. For example, although the concentric, circular crosssectional configuration of the housing, condenser unit and distributortube is preferred for its simplicity, economy, rugged construction andhigh efficiency of condensing and defrosting, it may be of rectangularor other cross sectional configuration if desired. Further, although theapparatus is shown mounted in a horizontal position, it may be mountedvertically or at intermediate angles. The tubular condenser unit may beconstructed in various ways other than the sectional arrangementillustrated. These and other modifications may be made, as desired,without departing from the spirit of this invention and the scope of theappended claims.

Having now described our invention and the manner in which it may beused, what we claim as new and desire to secure by Letters Patent is:

1. Vapor condensing apparatus, comprising (a) a hollow housing having aperipheral wall and front and rear walls and adapted to be evacuated tosub-atmospheric pressure,

(b) a tubular condenser unit in the housing spaced inwardly from theperipheral wall thereof, the rear end of the condenser unit beingpositioned closely adjacent the rear end of the housing, the front endof the condenser unit being open and terminating inwardly of the frontend wall of the housing, whereby the condenser unit defines with thehousing inner and outer chambers communicating with each other at thefront end of the housing,

(c) the condenser unit having passageway means therein for thecirculation of refrigerant fluid,

(d) refrigerant inlet and outlet conduit means connected at one end tothe condenser unit passageway means and extending through the housingfor connection to a circulating source of refrigerant fluid,

(e) outlet conduit means adjacent the rear wall of the housingcommunicating with the outer chamber and adapted for connection to asource of vacuum,

(f) a tubular vapor inlet extending inwardly through the rear wall ofthe housing and communicating with the inner chamber, the outer end ofthe vapor inlet being adapted for connection to a source of vapor to becondensed, and

(g) the vapor inlet including distribution means for distributing vaporsto be condensed substantially uniformly along the inner surface of thecondenser unit.

2. The apparatus of claim 1 wherein the distribution means comprises anelongated tubular vapor distributor spaced inwardly from and extending asubstantial distance into the inner chamber, the portion of thedistributor within the inner chamber being perforate for passage ofvapor outwardly therefrom into the space between the distributor andcondenser unit.

3. The apparatus of claim 1 wherein the peripheral wall of the housing,the tubular condenser unit and the tubular vapor inlet are circular incross section.

4. The apparatus of claim 1 wherein the condenser unit comprises aplurality of interconnected longitudinal sections each having passagewaymeans therein.

5. The apparatus of claim wherein the longitudinal sections are ofarcuate cross sections and are interconnected at their longitudinalmargins forming a condenser unit of substantially circular crosssection.

6. The apparatus of claim 1 wherein the condenser unit comprises aplurality of interconnected longitudinal sections each having passagewaymeans therein, and the refrigerant inlet and outlet conduit meanscomprises a plurality of inlet and outlet conduits one of each connectedat one end to one of the passageway means and the opposite end beingconnected to inlet and outlet header means, respectively, the headermeans being adapted for connection to a circulating source ofrefrigerant iiuid.

7. The apparatus of claim 1 wherein the front wall of the housingcomprises a door mounted on the housing for removably closing the frontend of the latter.

3. The apparatus of claim 1 wherein the front wall of the housingincludes a transparent window for viewing the interior of the apparatus.

9. The apparatus of claim 1 including liquid defrost drain conduit meansin the housing.

References Cited UNITED STATES PATENTS 2,358,940 9/1944 Schoeller 165l552,372,079 3/1945 Gunter 165-155 X 2,626,130 1/1953 Raskin 165-469 X2,870,997 1/1959 Soderstrom l-155 X ROBERT A. OLEARY, Primary Examiner.

A. W. DAVIS, Assistant Examiner.

